One of the main reasons it becomes very very tedious to do on alts is that it's a high number of days that you simply have to knock out quests to get to the reputation levels to spend valor.
You've made a couple of changes that help a little by moving one slot from each from revered to honored but the fact that there are still revered and even exalted rewards that many alts would desire to get, makes the current situation still way too cumbersome.
You mentioned before looking into a system where once you hit revered on a character, that reputation can be gained double on all your characters.
This would be great, if it was in the game now. You also didn't clarify if that counts for kill reputation, quest reputation or just daily reputation, or even the peace pipes.
Is there any estimate on when this will be available?
An alternative which would be easy(?) to implement and have less unintended side effects, would be to place on the reputation vendors, tokens that increase reputation.
At revered you can buy a token for gold that is bnet-account bound that you can expend to get up to honored rep, possibly halfway to reverered. This way you can 100% select which factions you want to make easier to gain on alts.